Infection is the major cause of morbidity and mortality in patients with malignant diseases. We are developing and evaluating the utility of various techniques and procedures to reduce the incidence of severe infection in cancer patients and other compromised hosts. The primary prophylactic technique under study is the laminar-air-flow type of isolation-filtration unit. We wish to learn whether this unit reduces the incidence of infection during chemotherapy, if patients undergoing such protection can tolerate more intensive chemotherapy, and if they consequently have an improved anti-tumor response. Other areas of interest include the improvement of methods by which occult infectious agents may be detected and eradicated; an evaluation of the acquired germ-free state and the influence of this state on physiologic and metabolic processes; and an evaluation of newer anti-viral and anti-fungal agents. In prospective trials, we are assessing the current etiology of febrile episodes in cancer patients, the most appropriate workup for fever in such patients, and the efficacy and toxicity of empiric antibiotic regimens offered for varying periods of time. Other studies concern the radioimmunoassay for candida antigen, the limulus assay for endotoxemia, and the pseudomonas aeruginosa vaccine.